Device for diverting fluid from a pipeline

ABSTRACT

A device for diverting liquid from a pipeline is described having a first conduit; a second conduit connected to the first conduit at at least a first location and a second location; with the second conduit having a first section to collect diverted liquid and a second elongated section adapted to contain at least parts of the diverted liquid with a hydrostatic head or level reactive to a pressure drop between the first and second location thus controlling flow of liquid from the first conduit through the second conduit by balancing the pressure drop with the hydrostatic head or level.

FIELD OF THE INVENTION

This invention relates to a device for diverting fluid from a pipelineand is particularly concerned with separating oil and water from amulti-phase flow of gas, oil and water.

BACKGROUND TO THE INVENTION

In the oil industry, the water-liquid-ratio (wlr) is an importantmeasurement of the output flowing from a well and for wells producing athree-phase flow (gas, oil and water) separator systems are used toseparate the gas, oil and water into individual streams to simplify thewlr measurement. However separator systems are heavy, bulky, costly andprone to failure and obtaining three separate streams for each componentcan be complicated and costly.

Where the liquid, i.e. water and oil, is not separated and metering isperformed on the multi-phase flow, the measurement of the wlr can bevery difficult, particularly when the volume fraction of gas in the lineis high. For example, where the wlr is 10% in a multi-phase flow with90% gas, then 1% of the total volume is water, 9% is oil and 90% is gas.Measurement of the wlr in a multi-phase flow requires detecting thepresence of the 1% by volume of water, whereas if all the gas is removedleaving an oil-water flow, measurement of the wlr requires detecting thepresence of the 10% by volume of water. Removing gas from themulti-phase stream to produce a liquid-rich stream therefore makesmeasurement of the wlr easier.

Hydrocyclones are used to produce a liquid-rich stream from amulti-phase flow. However these systems tend to be large and result inthe liquid and gas phases travelling in opposite directions which cancause problems with pipe layout.

It is an aim of the present invention to produce a device for obtaininga liquid-rich stream without the disadvantages associated with the priorart, and also aims to provide a device for retrofitting to existing flowmeters to increase their range of operation.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is adevice for diverting liquid from a pipeline, the device comprising afirst conduit, a second conduit connected across at least part of thefirst conduit, and means for controlling flow of liquid from the firstconduit through the second conduit by use of hydrostatic pressure.

Such a device is particularly applicable for surface pipelinestransporting gas-rich flows from wells, the flow being of around 90%gas, with the remaining percentage by volume consisting of oil andwater. The device is suitable for use as a flowmeter when used incombination with appropriate gauges, and also is such as to allowsampling as liquid can be tapped off separately to gas. The device isalso intended for retrofitting to existing flowmeters to increase therange over which flows can be measured, with the device acting toprovide an offset to these meters, or the device can be incorporatedinto the flowmeter during manufacture.

In use, the device is typically connected to a pipeline transporting amulti-phase flow which is predominantly made up of gas, with the firstconduit arranged to be substantially vertical relative to the earth'ssurface.

Therefore the first conduit in use is preferably connected between twosections of an existing pipeline. This particularly requires thepipeline flow to be stopped whilst the pipeline is cut to allow theplacing of the device.

The means for controlling flow of liquid from the first conduit throughthe second conduit is preferably provided by an S-shaped section withinthe second conduit. Thus the second conduit may incorporate the meansfor controlling the flow of liquid. By using an S-shaped bend andarranging the second conduit to provide a bypass route across a lengthof the first conduit, the pressure drop across the bypassed length ofthe first conduit will be balanced by a difference in the height offluid in the two curved sections forming the S-shaped bend. As a result,if more liquid is introduced into the second conduit, the level of fluidin the S-shaped bend alters to remain in equilibrium with the pressuredrop across the length of the first conduit, as a result of hydrostaticpressure, and thus new fluid introduced into the second conduit willforce fluid out of the S-bend and into a return section of the secondconduit thereby to return to the first conduit.

The second conduit may further comprise a collecting means placed atleast partly within the first conduit, and thus the second conduitpreferably further comprises an annulus extending inwards from an innerwall of the first conduit and a lip extending upwards from an innercircumference of the annulus, and acting to trap liquid travelling alongthe walls of the first conduit and direct liquid into the secondconduit.

The second conduit may comprise an elongate lip attached to the annulusor collar, with the elongate lip forming a baffle plate to act toseparate liquid from the gas flow.

Preferably the first conduit is provided with an inlet at substantiallyright angles to the first conduit. This tangential inlet ensures that inuse fluid passing into the first conduit gains a certain degree ofcentrifugal force to further assist with separation of liquid componentsfrom the gas.

The collecting means may further comprise receptacle means incommunication with the first conduit and the annulus. This allows avolume of liquid to be stored before the liquid enters the S-shapedsection, and so provides time for gas inadvertently trapped in theliquid to escape the liquid whilst it is held in the receptacle meansprior to entry into the S-shaped section, the gas then returning to thefirst conduit.

The receptacle means is preferably placed adjacent to the annulus andthe first conduit, and connected thereto by first and second passages.

Alternatively the receptacle means surrounds the annulus and at leastpart of the first conduit with two spaced apart apertures in an encasedwall of the first conduit providing communication between the receptaclemeans, annulus and first conduit.

The second conduit may further comprise an elongate section extendingfrom an end of the S-shaped section furthest from the first conduit, theelongate section providing a generally downward path and joining withthe first conduit at a distance below an inlet to the second conduit.

The second conduit may comprise a delay section leading from thecollecting means and joining with a first end of the S-shaped section,the delay section comprising a hollow cylinder of tapering cross sectionwhich is wound around the first conduit to form a spiral.

The device is suitable for use with surface pipes, but may be adaptedfor use on a vertical well pipe such as a borehole.

BRIEF DESCRIPTION OF DRAWINGS

The invention is now described, by way of example, with reference to thefollowing drawings in which:

FIG. 1 shows a section through a first embodiment of a device inaccordance with the present invention;

FIG. 2 shows a sectional view on the line II—II of FIG. 1;

FIG. 3 shows a section through a second embodiment of a device inaccordance with the present invention;

FIG. 4 corresponds to FIG. 3 and is used to explain operation of thedevice;

FIG. 5 is a graph illustrating the amount of liquid extracted as apercentage of liquid input for the device shown in FIG. 3;

FIG. 6 shows a section through of a third embodiment of a device inaccordance with the present invention;

FIG. 7 shows a section through a fourth embodiment of a device inaccordance with the present invention;

FIG. 8 shows a section through a fifth embodiment of a device inaccordance with the present invention; and

FIG. 9 shows a schematic diagram of a flowmeter incorporating a devicein accordance with the present invention.

DESCRIPTION

A device 10 in accordance with the present invention is illustrated inFIG. 1. Typically the device is inserted into a surface pipelinecarrying a multi-phase flow of gas, oil and water from a well. To insertthe device, the flow in the pipeline is stopped, and the pipeline cutand modified so that an upstream portion of pipeline feeds into an inlet12 of the device with a downstream portion of the pipeline connected toan outlet 14 of the device. The device is placed at right angles toground level.

The device 10 is made from metal and comprises a first conduit 20 and asecond conduit 22. The first conduit 20 has a circular cross-section oftypically the same size as the cross-section of the pipeline, whilst thesecond conduit 22 has generally a substantially smaller circularcross-section than the first conduit. The walls of the first and secondconduits are of a suitable thickness to withstand the pressuresassociated with multi-phase production flows, and thus are typically ofa thickness that will withstand 5000 psi.

The second conduit 22 is connected across a length L of the verticalfirst conduit 20 so providing a path along which liquid can betemporarily diverted from the main conduit, entering inlet 24 beforereturning to the main conduit at outlet 26. The second conduit 22comprises a collecting means 30 joined to the inlet 24 and which sitswithin the first conduit 20, a first elongate section 32 of pipeattached between the inlet 24 and a first end 34 of an S-shaped section36, a second elongate section 38 joined to a second end 40 of theS-shaped section, and a downwardly slanting section 42 leading from thesecond elongate section to the outlet 26 and joining to the firstconduit 20. The collecting means 30 comprises an annulus 44, of the sameouter diameter as the first conduit, and a lip 46 extending upwards froman inner edge 50 of the annulus 44.

FIG. 2 shows a sectional view along line II—II of FIG. 1 from which canbe seen the cross-section of the second conduit 22, excluding thecollecting means, and the cross-section of the first conduit 20 arecircular, with the diameter of the first conduit 20 being substantiallygreater than the diameter of the second conduit 22.

When a multi-phase flow travels in a pipeline, the liquid in the flow,i.e. oil and water, predominantly travels along the walls of thepipeline as a result of frictional effects. Thus by placing an annulus44 with a lip 46 within the first conduit 20, the liquid portion of thegas-liquid flow is channelled into the second conduit 22. In theembodiment shown in FIG. 1, some gas will pass with this liquid into thesecond conduit 22, but, as will be explained later, due to the residencetime of liquid within the S-shaped section 36, much of the gas willreturn to the first conduit 20.

A second embodiment of the device is shown in FIG. 3, and comprises amain conduit 50 and a secondary conduit 52 incorporating a more complexcollecting means 54 than that of the first embodiment. Instead of flowfrom the pipeline travelling down into the first conduit, i.e. withgravity, a tangential inlet 56 to the main conduit 50 is provided. Thesecond collecting means 54 comprises an annulus 58 with an elongate lip60 which extends up beyond the tangential inlet 56 so as to act asbaffle plate, and a substantially enclosed cylinder 62. The cylinder hasa lower inlet 64 which joins with the first conduit 50 and so connectsto the annulus 58 as well, and an upper inlet 66 placed further up thewall of the first conduit. The remainder of the second conduit comprisesa first elongate section 70, an upper end 72 of which extends up andinto the cylinder 62 and is open to receive liquid, with a lower end 74attached to a first end of an S-shaped section 80. A flared elongatesection 82 joins to a second end of the S-shaped section 80 and leadsinto a downwardly slanting section 84 which in turn connects with ahorizontal portion 86 of pipe meeting the first conduit 50 at a positionbelow the collecting means. An anti-siphon line 90 is provided betweenthe flared section 82 and an uppermost end 92 of the first conduit 50 soas to ensure that automatic siphoning of the liquid through the systemdoes not occur. The dimensions of the device are approximately 1200 mm(high)×500 mm×500 mm.

This embodiment has enhanced gas rejection over the first embodiment asthe passage time of the liquid through the device is increased due tothe increased volume of the collecting means. In addition, thetangential inlet imparts a certain degree of centrifugal force to thefluid as it enters the first conduit and this produces a swirling effectin the flow which assists with separation of liquid from gas. The baffleplate also acts to increase separation of liquid from gas as, when themulti-phase flow hits the baffle plate, the passage of liquid isabruptly halted causing the liquid to fall to the base of the collectingannulus. However the gas is not so affected and passes along the lengthof the first conduit.

The operation of the device will now be described with reference to FIG.4, which uses common reference numerals to FIG. 3 where appropriate. Thedevice uses the principle of hydrostatic pressure to provide acontrollable passage of liquid through the system, eventually to returnto the first conduit. The device thus avoids the need for any movingparts or any external control for the device to operate. When amulti-phase flow enters the first conduit 50 via the tangential inlet56, liquid incident on the baffle plate 60 falls down to the collectingannulus 58 and, due to the interconnection of the annulus, cylinder 62and S-shaped bend 80, will pass into all these parts of the secondconduit. Gas in the multi-phase flow is largely unaffected by thepresence of the baffle plate 60 and generally will simply continueflowing along the length of the first conduit, although some gas will betrapped in the liquid falling into annulus 58.

A pressure drop exists in the first conduit 50 due to gravity, with gasat the upper end 92 of the conduit being at a lower pressure P₁ than gasat a lower end 94 of the conduit which is at pressure P₂. The pressuredifference, P_(1−P) ₂, of around 100 mbar is balanced by the head ofliquid in the S-shaped bend 80, i.e. the pressure exerted by the liquidh_(liquid)−h₀. Thus in the equilibrium position where fluid has beenintroduced into the second conduit but where, for example, flow has thenstopped, the height of liquid in the S-shaped bend is greater than theheight of the liquid in the collecting means by an amount that balancesthe pressure difference.

As more liquid is introduced into the collecting portion of the conduit,the system moves out of equilibrium. Thus the level of liquid in thecylinder and annulus will be such that the head of liquid does notbalance the pressure drop ΔP. The system will act to restore theequilibrium state and thus increase the level of fluid in the S-bend toh_(level) so as to ensure that the head balances the pressure drop.Liquid is thus forced up and out of a vertical portion 96 of the S-bendand into the flared portion 82 to return to the first conduit, as thesystem continuously acts to restore equilibrium as liquid flows into thesecond conduit. The maximum liquid extraction flow rate is a function ofthe dimensions of the device, but for a device of dimension 1200 mm×500mm×500 mm is typically 8 m³ an hour.

To explain in more detail, the equilibrium state is thus when no liquidis extracted and the hydrostatic head, ρg(h_(Level)−h₀) is balanced bythe pressure drop P_(1−P) ₂:ΔP=P ₁ −P ₂ =ρg(h _(Level) −h ₀)  (1)where ρ is the liquid density, h_(Level) is the greatest height ofliquid in S-shaped section 80 of diameter d, and h_(liquid) is theheight of liquid in the cylinder which has diameter D.

For a liquid velocity of ν₁ in diameter D, the velocity ν₂ in diameter dis $\begin{matrix}{v_{2} = {v_{1}\frac{D^{2}}{d^{2}}}} & (2)\end{matrix}$

When h_(Liquid)>h₀ then liquid flows through the device and with aliquid velocity in diameter D of ν₁, the liquid velocity ν₂ in diameterd, can be written as $\begin{matrix}{{v_{2} = \sqrt{\left( \frac{2}{\rho} \right)\frac{\left( {{\Delta\; P} - P_{Losses} - {\rho\;{g\left( {h_{Level} - h_{Liquid}} \right)}}} \right)}{\left( {1 - \frac{d^{4}}{D^{4}}} \right)}}}{where}} & (3) \\{P_{Losses} = \frac{2\; f\;\rho\; v_{2}^{2}L_{Losses}}{d}} & (4)\end{matrix}$andf=aRe ^(−b) Blasius formula, a=0.079, b=0.25  (5)and $\begin{matrix}{{Re} = \frac{\rho\; v_{2}d}{\eta_{liquid}}} & (6)\end{matrix}$where P_(Losses) is the pressure loss in diameter d, L_(Losses) theequivalent straight pipe length diameter d, and η_(liquid) the viscosityof the liquid.

When ν₂=0 then P_(Losses)=0, and ΔP is given by equation (1). h₀ shouldbe chosen to be large enough so that no liquid enters the liquid leg, inwhich case $\begin{matrix}{{v_{2} = \sqrt{\left( \frac{2}{\rho} \right)\frac{\left( {{\rho\;{g\left( {h_{Liquid} - h_{0}} \right)}} - P_{Losses}} \right)}{\left( {1 - \frac{d^{4}}{D^{4}}} \right)}}}{{{{For}\mspace{14mu} v_{2}} > 0},{{{{then}\mspace{14mu} P_{Losses}} < {\rho\;{g\left( {h_{Liquid} - h_{0}} \right)}}} = 0}}} & (7)\end{matrix}$

The maximum value of ν₂ (or equivalently the maximum liquidextracted=ν₂πd²/4) is driven by h_(Liquid) and this determines the totalheight of the device.

Thus if there is only gas in the main flow line then the equilibriumstate is when the hydrostatic pressure difference between h_(liquid) andh₀ equals the pressure difference between the top of the first conduitand where the second conduit returns to join the first conduit. If thehydrostatic pressure of the liquid head is less than ΔP, then fluid willflow over the top bend of the S-shaped section and return to the mainflow line via sections 82, 84, 86.

This system is self regulating in that liquid will only flow out of theS-bend section when liquid is in the annulus, cylinder and S-shapedsection and the hydrostatic head, h, is too small to balance thepressure difference ΔP. Hence a heavy liquid phase will flow through thedevice, if there is only gas in the main flow line there will be no flowthrough the device, and the device rejects gas.

As mentioned previously, some gas will be trapped with the liquid whenit is collected from the first conduit, and to ensure that the wlrmeasurement is easy to perform, as much gas as possible needs to bereturned to the main conduit. A delay time, or lag, before liquid entersthe S-shaped section is desirable so that gas caught within the liquidcan escape.

There are a variety of ways of producing such a delay, with the secondembodiment achieving this by increasing the volume of liquid waiting topass into the S-shaped section.

The increased residence time of the liquid in the collection meansallows gas bubbles trapped within the liquid to have an extended time inwhich to rise to the surface of the liquid and return to the firstconduit by means of the first conducting passageway 66. There are otherways of increasing the residence time, and these are discussed withreference to FIGS. 6 and 7. Ideally the residence time is around 5 s orsuch that the time for gas to rise to the surface of liquid in thecollection means is less than the time for fluid to pass from thecollection means to the S-shaped bend. The residence time needed dependson the distance the gas has to travel through the liquid to reach aliquid-gas interface and the velocities of the gas and liquid phases.

The devices discussed herein selectively divert liquid from amulti-phase flow so that the wlr can readily be measured, without alarge proportion of gas being associated with the liquid and interferingwith the measurement. The devices have many uses in that they allowdirect sampling of the liquid by placing valves at positions A and B,and easy measurement of liquid and gas flow rates by placing a gas flowmeter at position C and a liquid flow and/or wlr meter at position D.The devices can also be used as a sandtrap by placing a valve at E todraw sand out of the base of cylinder 62, and the devices can be used toprovide liquid removal from a flow by pumping liquid out of the devicefrom any point in return path 82, 84, 86 before the liquid returns tothe main conduit. The device can also be used as a compact separator ofliquid for multi-phase flows.

In situations where a representative liquid sample is required thecollection means is positioned in an area of high mixing of gas andliquid.

The devices can also be used for measurement of oil shrinkage, cleaningof the system by fluid injection, and calibration of any meterpositioned at D by injecting fluids of known properties at knownvelocities.

Local heating can also be used to increase the flow of viscous fluidsthrough the device.

Enhanced liquid removal can be achieved by careful design of the flowconditions upstream of the device and by positioning two or more devicesin series.

With a device such as shown in FIG. 3, it is possible to extract around90% of the liquid in a liquid gas flow. This is illustrated by the graphof FIG. 5 which plots the “liquid extracted” against “the liquid inputinto the first conduit” for a variety of different water liquid ratiosranging from glr (gas volume rate/liquid flow rate) less than 10 and gvf(gas volume rate/total volume) less than 0.91, up to glr in the range of200–1000 and gvf in the range 0.995–0.999. The liquid extracted has lessthan 1% gas entrained.

FIG. 6 shows a further embodiment of a device in accordance with theinvention where a cylinder 100 surrounds a portion of a first conduit102 with upper 110 and lower 112 apertures in plate 114 providingcommunication paths for gas and liquid between a collecting annulus 116and the first conduit 102.

FIG. 7 illustrates another embodiment of the present invention, where toincrease residence time of fluid in the device, a tapering cross-sectionpipe 120 is wound around a first conduit 122 to lead into an S-shapedbend 124. The diameter of this pipe 120 and the pitch of the winding aresuch that the flow in this pipe is stratified with the liquid on thelower surface of the pipe. In this case, any gas in the liquid has totravel a distance equal to the thickness of the liquid stratified layerbefore exiting via the collecting means 126. Having a pipe with adecreasing diameter enhances this effect. This ensures that the liquidcollected within the S-bend is to a large extent gas free.

A further embodiment is illustrated at FIG. 8, this being a device foruse in an operational well 130 with fluid flowing up to surface as shownby arrow 132. By providing low pressure at one end 134 of the device,liquid collection can be achieved in a similar manner as aforesaid.

A device in accordance with the present invention can also be used tomodify existing flowmeters so as to extend their range of operation, andthis is shown in FIG. 9.

Multi-phase flowmeters are used in the oil industry to measure the flowrates of oil, water and gas in a pipeline without separating the phases.These meters have an operational range with a lower limit that cangenerally only be modified by a change in dimensions or by use ofadditional meters. One way of lowering the operating range of amulti-phase meter therefore involves a second multi-phase meter inseries with the first. In the cases where the oil, water and gas phasesare separated into individual streams, lowering the range involvesadding additional meters to each flow line: this is costly as the numberof meters needed is doubled and each meter is expensive. However inaccordance with another aspect of the present invention, a device ingenerally the same form as that discussed previously is fitted to,either on manufacture or by retrofitting, a multi-phase meter so as toincrease flow by a known amount that allows the meter to function overan increased operating range.

Such a modified flow meter 138 is illustrated schematically in FIG. 9.The basic flow meter is described in Atkinson, I., Berard, M. B-VHanssen, G Segeral: “New Generation Multiphase Flowmeters fromSchlumberger and Framo Eng.AS.,” 17^(th) International North Sea FlowMeasurement Workshop, Oslo, Norway, October 1999. A multi-phase flow 140is fed into an input 142 of the flowmeter and passes through the meterto outlet 144. A device 150 in accordance with the invention, such asthat depicted in FIG. 3, is inserted in the outlet, or downstream, pathof the meter and the device used to divert liquid from the multi-phaseflow, the liquid passing along path 152 to a liquid storage tank 154.Any gas contained in the liquid is returned along line 156 to the outletpath. The liquid in the liquid storage tank 154 is fed back along line158 to the inlet 142, and upstream of the metering section 159, by pump160, and the amount of liquid fed back is monitored by liquid flow meter162.

This increases the total liquid flow through the multi-phase meter by ameasured amount such that the flow through the meter is within theoriginal operating range. The actual flow in the main pipeline iscomputed from the difference between the flow measured by themulti-phase meter and that measured by the meter in the liquid line. Theflow ‘returned’ is only liquid phases to simplify the metering andpumping operation as then metering can be performed with a liquid meterand standard liquid pump. The accuracy of the liquid flow rate will bedecreased slightly as a result of using two meters, for example, if theaccuracy of the multi-phase meter is ±5% and the liquid meter is ±2%then the final accuracy of the combined meter will be ±5.4% (using RMSmethod).

The size of the tank 154 depends upon the efficiency of the device 150,the liquid volume rate required to be pumped to get the multi-phasemeter within its operating range, and the measurement time of themulti-phase meter.

The above-described embodiments are illustrative of the invention onlyand are not intended to limit the scope of the present invention.

1. A device for diverting liquid from a pipeline, the device comprising:a first conduit; a second conduit connected to the first conduit at atleast a first location and a second location; said second conduit havinga first section to collect diverted liquid and a second elongatedsection adapted to contain at least parts of the diverted liquid with ahydrostatic head or level reactive to a pressure drop between the firstand second location thus controlling flow of liquid from the firstconduit through the second conduit by balancing the pressure drop withthe hydrostatic head or level.
 2. A device according to claim 1, whereinthe assembly for controlling flow of liquid from the first conduitthrough the second conduit comprises an S-shaped section within thesecond conduit.
 3. A device according to claim 1, wherein the firstconduit is provided with an inlet at substantially right angles to thefirst conduit.
 4. A device according to claim 1, wherein the firstsection of the second conduit further comprises a collector placed atleast partly within the first conduit.
 5. A device according to claim 4,wherein the collector comprises an annulus extending inwards from aninner wall of the first conduit and a lip extending upwards from aninner circumference of the annulus.
 6. A device according to claim 5,wherein the lip is elongate and extends upwards to an inlet of the firstconduit, so as to act as a baffle plate.
 7. A device according to claim5, wherein the collector further comprises a receptacle in communicationwith the first conduit and the annulus.
 8. A device according to claim7, wherein the receptacle is placed adjacent to the annulus and thefirst conduit, and connected thereto by first and second passages.
 9. Adevice according to claim 7, wherein the receptacle surrounds theannulus and at least part of the first conduit with two spaced apartapertures in an encased wall of the first conduit providingcommunication between the receptacle, annulus and first conduit.
 10. Adevice according to claim 2, wherein the second conduit furthercomprises an elongate section extending from an end of the S-shapedsection furthest from the first conduit, the elongate section providinga generally downward path and joining with the first conduit at adistance below an inlet to the second conduit.
 11. A device according toclaim 4, wherein the second conduit comprises a delay section leadingfrom the collector and joining with a first end of the S-shaped section,the delay section comprising a hollow cylinder of tapering cross sectionwhich is wound around the first conduit to form a spiral.
 12. A deviceaccording to claim 1, wherein the first conduit is part of a pipelineconnected to a borehole.
 13. A device according to claim 1, wherein ananti-siphon line connects the second conduit with the first conduit. 14.A flow meter fitted with a device according to claim
 1. 15. A deviceaccording to claim 1 wherein the second conduit joins the first conduitat the second location.
 16. A device according to claim 1 wherein thesecond conduit includes a third section downwardly slanted towards thesecond location to join the second conduit with the first conduit.